Process of smelting finely divided sulphide ores



Patented Nov. l5,- 1932 -UNrrlezD STATES PATENT' OFFICE- l nomen rnnmum, or sHAwnneAN FALLS, nunnnc, emana, Assmann To m sunrmnn nnsnnnpn CORPORATION, Lmxrnn, vor MONTREAL, camina.' A concu- TION 0I CANADA.

- nocnss or sunLr'ING animar nrvrnnn sunrnrnn onus` Application filed .Tune 15, 1929, Serial No. 371,123. Renewed August 8, 1938.

This invention relates to a process of smelting metals from sulphide ores, and relates more particularly to smelting ores such as those of copper and lead, which by interaction with oxygen or oxides can be made to yield the metallicelement. Y One of the objectsof the invention is to enable the smelting of finely divided ores such as flotation concentrates. Another object of the invention is to accomplish in a single step and in a single apparatus the roasting and reduction steps which are usually sequentially performed. Still another object is to enable the smelting of sulphide ores to be accomplished with much less fuel than. ordinarily used or even without consumption of added fuel. Various other objects and the advantages of the invention will be ascertained from the following description.

The method usually employed in smelting` sulphide ores, such as those of copper or lead, is to first roast the ore to the extent of removing only a portion of the contained sulphur and leaving in the roasted ore sufcient sulphur to combine with oxygen which has been fixed during the roasting step. The roasted ore'is then smelted with silicious flux in a furnace in such manner that the oxygen and the remaining sulphur react and pass off in gaseous products while the iron usually present in the ore combines in the form of an oxide with the added silica-,giving a slag' from beneath which the base metal is run off.

In smelting copper ore, itis usual to regulate the roasting so as to leave an excess of sulphur, with the resultthat the product of thesmeltingoperation 1s copper matte, from which the sulphur is later removed by the well known converting process to yield crude metallic copper.

The reactions in both the first and second steps are to some extent exothermic, but because of elapse of time between .the two steps the usual method just described.

In my former application, Serial Number' rounding the stack.

333,222, filed January 17th, 1929, there is disclosed a 'process' of and apparatus for 'combustion of finely. divided metallic sulphldes for the production of sulphur dioxide.

-The operation of that process with iron sulphide yields as another product a sintered mass of high metalcontent.

Briefly, the" 1process consists in discharging a jet ofthe nely divided sulphide with a measured amount of air into the top of a furnace where the sulphide burns yielding sulphur dioxide `particular reference, as aforesaid, to'treatment of sulphides, such as those of copper and lead, which by interaction with oxygen or oxides can be made to yield the metallic element, and involves the regulation of air supply and combustion of the sul hide to the end that the heat of oxidation o the suli phur and of the iron and of the interaction of the iron oxide and silica is utilized to,

smelt and also to reduce the ores to metallic condition in a single step.

One form of apparatus found suitable for putting the process intooperation is illustratecl in the accompanying drawing, but it will be understood that the invention is not confined to the .apparatus illustrated, as modications may be made or other forms of apparatus used.

Referring to the drawing, 11 designates a furnace of suitable dimensions, formed of refractory material and having a tap hole 12 at or near the bottom. The top 13 of the furnace, which is also formed of refractory material, is providedwith a central ingress opening 14 and an eccentric egressopening 15. A stack 16 leads from the egress opening-for escape of gaseous and vaporous products of combustion. This stack includes any suitable form of heat interchange apparatus, herein indicated merel -as a jacket 17 surblower 18 supplies air through a conduit 19 into the upper end of the heat interchanger and, after heating, the air passes through a conduit 20. It will `be observed that the'airand hot gases flow contrawise, so that the greatest heating efflciency is realized. The conduit 20 leads to a sul hide injecting nozzle 21 of any suitable esign and construction, which projects through the ingress opening 14 of the furnace roof and is arranged to direct a jet of sulphide and air downwardly into the fur- The construction of the nozzle is referably such that the jet of air and pow ered sulphide is given a mixing action, so that the flame will be continuous' and steady. Dry owdered sulphide ore is supplied to the nozz e from a hopper 22 through a conduit 23 in which a suitably driven screw conveyor 24, or other suitable device, operates to advance the ore at any suitable regular rate. A baffle 25 in the upper part of the nozzle serves to direct the air downwardly and prevent it blowingout through the conduit 23 and the hopper. A pipe 26 leads into the nozzlefor admission of fuel.V

In detail, the process and operation of the apparatus are as follows The furnace having been suitabl preheated, air and finely divided dry su phide ore are admitted to the nozzle,l the air being preheated by passage through the heat interchanger 17. The jet lof air and ore from the nozzle'i ites or is ignited and the fiame burns within the furnace., The rate of air admission relatively to the rate of sulphide admission is such that sufficient oxygen is supplied to loxidize all the sul hur in the sulphides and all of the iron. ilicious flux for the iron may be added along with the sulphides.. `This flux may conveniently be sand or round silica. Alternatively, the iux may e added in lump or other form separately from the sulphide ores. The metal sulphides being in inely divided form are rapidly burned and heated as they fall to the bottom or hearth of the furnace and are at the same time largely or completely desulphured. Heat is evolved in the upperv part of the furnace by oxidation. of the sulphur and of the iron and additional heat is evolved on the hearth ofthefurnaceby reaction of iron oxide and silica. In some cases, sufficient heat 'will be realized to accomplish` smelting with production of a high grade molten matte or of crude molten metal and a fused slag. When the heat available (includingthat recovered in the heat exchanger) is not sufficient for smelting, additional heat may be obtained by introducing fuel such as oil or powdered coal through the pipe 26 or by any'other suitable means.

It is essential to admit only sufficient air for oxidation of the sulphur and iron and the fuel, should any be used, if oxidation of the desired product is to be avoided.-

It will be understood that the amount yof heat realizable from the exothermic reactions in the operation of this process depends Chiefl upon the character of the ores treated. gres with high heat value ma liberate enough heat, so that by reason o the heat conservation and concentration in this process due to complete oxidation of sulphur and iron in a single step, the copper or lead content may be smelted out without the use of added fuel. By recovery of heat in the exchanger in. addltion to the conservation and concentration as above, ores of lower heat value may be smelted without use of added ".uel and ores of still lower heat value may be smelted, by reason'of the heat conservation, concentration and recovery, with materially less expenditure of fuel than is possible by previously known methods'. In smelting a copper -lotation concentrate containing 25% copper, 30% sulphur and 40% iron and using cold air for the blast the flame temperature in the furnace will be about 90.0 C. which is not high enough to accomplish smelting. By preheating the air in an ecient exchanger, the additional heat neces- Y sary for smelting may be obtained. Nevering and smelting steps may be accomplished in a single step, in a single apparatus, in a continuous manner and with the use of less fuel than ordinarily or of no fuel at all. It will be seen further that finely divided ores diiicult or impossible to treat by other processes may be successfully treated by this process, since the ore particles entering the furnace through the nozzle are at once suiciently separated to permit of their being individually fully enveloped and quickly treated in .the stream of fresh preheated air.

Having thus described my invention, what I claim is 1. A continuous process of smelting copper or lead sulphide ores, whichV by interaction v with oxygen or oxides will yield the metallic element, which comprises, introducing fuel together with the ore and a flux into a furnace heated to a temperature at which smelt- 'ing will occur, the ore being in finely divided state and introduced continuously and substantially vertically downwardly through the furnace roof by means of a current of oxidizing gas not more than is substantially sufficient in amount for oxidation of all the sulphur, iron and fuel present, said gas being preheated to such temperature as will, with the heat evolved from combustion of the sulphur, iron and fuel and from the combination of iron oxide and flux, maintain a temrature in the furnace suiiicient for smelts 1n of the ore in a single step to a fluent met "c body on the bottom of the furnace, the gaseous products of combustion being removed through the furnace in a direction p contrawise to the movement of ore and oxidizlo ing as, and vutilizing heat from said gaseous pr ucts after theasame have been removed t from the furnace, to preheat said oxidizing. 'y

2. A continuous process of smelting copper or'le'ad sulphide ores, which b interaction with oxygen or oxides will yiel the metallic element, which comprises, introducing fuel together with the ore and a flux into a furnace heated to a temperature at which smeltm ing will occur, the ore being in finely divided hand.

state and introduced continuously and substantially directly downwardly from the furnace roof by means of a current of oxidizing gas not more than is substantially suicient in z5 amount for oxidation of al1 the sulphur, iron and fuel present, said gas being preheated to such temperature as will, with the heat evolved from combustion of the sulphur, iron and fuel and from the combination of iron oxide and flux, maintain a temperature in the furnace suiiicient for smelting of the ore in a single step to a fluent metallic body at the bottom of the furnace, the gaseous products of combustion being removed through the 85 furnace in a direction contrawise to the movement of ore and oxidizing gas.

3. A continuous process of smelting copper or lead sulphide ores, which by interaction with oxygen or oxides will yield the metallic element, which comprises, introducin fuel together with the ore and aflux into t e top of a furnace heated to a temperature at which smelting will occur, the ore being substantially continuously introduced in a finely divid'ed state and being carried substantially directly downwardlywithin the furnace by means of a current of oxidizing gas not more than is substantially suiicient 1n amount for oxidation of all the sulphur, iron and fuel present, said gas being preheated to such temperature as will, with the heat evolved from combustion of the sulphur, iron and fuel and from the combination of iron oxide and flux, maintain a temperature in the furnace suilicient for smeltin of the ore in a single step to a `fluent metalhc body at the bottom of the furnace, the gaseous products of combustion being removed at the u per part of the furnace after passage of t e same through the furnace in a direction substantially contrawise to the movement of ore and oxidizing gas- In witness whereof, I have hereunto set my HORACE 

